1. Field of the Invention
This invention relates to logic elements in general, and to a non-contemporaneous logic element in particular. Contemporaneous, i.e. combinational, logic elements are widely applied in fields such as computation and machine control. Sequential logic elements are similarly applied, and they are combinations of contemporaneous logic elements which, generally, are stepped through their paces by means of clock pulses.
This invention identifies one of a new class of logic elements which are responsive to non-contemporaneous input signals; and a method of synthesizing conditions corresponding to such temporal sequences.
2. Description Relative to the Prior Art
The definitions of combinational, i.e. contemporaneous, logic elements; and sequential logic elements are given in the IEEE Standard Dictionary of Electrical and Electronics Terms, 1972, Wiley-Intersciences:
(A) Combinational Logic Element: 1. a device having zero or more input channels and one output channel, each of which is always in one of exactly two possible physical states, except during switching transients. The output channel state is determined completely by the contemporaneous input channel state combination (to within switching transients).
(B) Sequential Logic Element: a device having at least one output channel and one or more input channels, all characterized by discrete states, such that the state of each output channel is determined by the previous states of the input channels.
The combinational logic elements provide outputs coexistent with the input signals (neglecting propagation delays), while the sequential logic elements provide outputs at the next clock pulse, according to inputs present during the preceding clock pulse.
In the fields of computation and machine control, there are certain instances when it is useful and necessary to have a logic element which provides a unique output in response to a non-contemporaneous, non-repetitive series of diverse input signals, i.e., a specified sequence.
In a particular application, for example, suppose it is necessary to ascertain in which order two sensors are activated, i.e., for two sensors "A" and "B", whether the sequence was "A" first, then "B", or the opposing order, "B" first, then "A". The application in an instance may be to implement an exercise in statistical analysis in which a given likely sequence is tabulated during a number of trials to determine its frequency.
Another application may be the determination, through fluidic sensors and logic elements, of the order in which two parts were installed on an assembly line.
Yet another application may be to perform a temporal decision test within a computer by means of an on-board, integrated circuit, implementing such statements as: "IF A BEFORE B THEN GO TO 235".
A logic element which can perform such tasks has not been readily available in the field, nor has such a class of logic elements been designated or defined.